The present invention relates to a navigation device, and particularly to a route search technique for a car-mounted navigation device.
For the purpose of relieving traffic jams or the like, a system exists in which vehicles running in some area (chargeable area) are charged. In this regard, Patent Document 1 describes a technique of trying to search for a route that bypasses a chargeable area when a present location is within a predetermined distance from the chargeable area.
Patent Document 1: Japanese Non-examined Patent Laid-Open No. 2003-35546
However, in some cases, a suitable bypass route cannot be found if the bypass route is searched for after a vehicle approaches a chargeable area. For example, there is a case where no intersection exists up to the chargeable area so that a bypass route can not be found, or a case where a very long bypass route is retrieved. On the other hand, even if a bypass route that does not pass a chargeable area is retrieved before departure and the retrieved bypass route is used for guidance, it does not always satisfy the needs of a user. Sometimes a user wants to determine whether he will take the bypass route, not at the time of departure but at the time when a chargeable area is approached. For example, when a car approaches a chargeable area, a user may take the bypass route if he still has time. However, he may consider that there is no other choice but to pay the charge, if he does not have enough time. The technique of Patent Document 1 cannot satisfy such needs of a user.
An object of the present invention is to provide a technique of presenting a suitable bypass route with appropriate timing when there is an area that will be probably avoided.